Pronoun set contexts

[pedantic-git]

When people have multiple pronoun sets, they often have contexts they use them (for example, "they/them with the cis, he/him with other trans folk").

While we can now reorder pronouns in name.pn (#13), there's no way to specify these contexts yet. Now the relationship between a user and their pronouns is a first-order model, it would be trivial to add this to the schema, but the question is what does a good UI look like?

Much of the conversation here has already happened on #13 but I'm moving this part of the issue to an issue in its own right.